Stators of rotary electric machines have a plurality of split cores. Each of the split cores comprises an arcuate yoke and a pole extending radially inwardly from the stator, with a coil wound on the pole.
The rotary electric machines with such stators are required to maximize the volume that the coil takes up in a slot defined between adjacent split cores. To meet such a requirement, it is necessary to wind more turns of the coils around the respective split cores. There have been proposed conventional techniques, described below, for increasing the volume that the coil takes up in each slot.
According to the first conventional technique, coils are wound around adjacent cores such that the coils have different cross-sectional shapes, filling slots defined between the cores with the coils (see Japanese Laid-Open Patent Publication No. 2000-14066 and Japanese Laid-Open Patent Publication No. 11-32457).
According to the second conventional technique, the width of a coil that is first inserted into a slot defined between adjacent cores is set to ½ or more of the opening width of the slot, and the coil has a slanted cross-sectional shape to avoid interference between the coil and a coil that is subsequently inserted into the slot (see Japanese Laid-Open Patent Publication No. 4-150749).
According to the third conventional technique, coils wound respectively around adjacent cores have different cross-sectional shapes (see Japanese Laid-Open Patent Publication No. 9-84287 and Japanese Laid-Open Patent Publication No. 10-174331). Specifically, one of the coils has a width that is progressively smaller toward the axis of the stator (the rotational axis of the rotary electric machine), and the other coil has an elongate rectangular cross-sectional shape and is inserted into a slot.